Abstract
The global proliferation of marine artificial habitats is rapidly altering the physical structure of coastlines, with knock-on effects on physical, chemical, and ecological processes at seascape scales. Ecological consequences of maritime sprawl associated with aquaculture are poorly understood, despite the fact that these suspended structures are particularly prone to biofouling, which can affect the industry and seascape around it. We characterised seascape-scale spatial and temporal distribution patterns of 10 biofouling taxa in relation to the presence and distance to Perna canaliculus mussel farms in New Zealand’s largest aquaculture region. Seven of 10 taxa had significantly higher cover on farms than in natural habitats throughout the region. The cover of 4 of those 7 taxa, including the high-profile pests Mytilus galloprovincialis and Undaria pinnatifida, exponentially decreased with distance from the nearest farm, while some taxa were absent from natural habitats (e.g. the ascidian Ciona robusta). In contrast, several opportunistic macroalgal species, such as Cladophora ruchingeri and Pylaiella littoralis, had colonised extensive areas of natural habitat. Our results suggest that biofouling is a persistent issue on mussel farms and that farm structures may act as reservoirs or ‘stepping stones’ for the dispersal of potential marine pests. These distributional and dispersal patterns can inform integrated pest management efforts focusing on spatial management strategies, such as ‘firebreaks’ in farm connectivity, avoidance of pest hotspots, and farm fallowing.
Highlights
Urban sprawl and the development of agricultural landscapes have had profound impacts on the distribution of organisms and the ecology of ecosystems, promoting certain species and processes that have thrived in highly modified and managed landscapes, while diminishing or eliminating others (Vila & Ibáñez 2011)
The exceptions were Colpomenia spp., which had similar cover in both habitat types (p > 0.05, Fig. 4, Table S1), and Pylaiella littoralis and Styela clava, which were more prevalent in natural habitats than on farms (p < 0.001, Fig. 4, Table S1)
M. galloprovincialis was the most abundant and prevalent focal taxon found across the study area, present on all farms surveyed and 71% of natural habitat transects
Summary
Urban sprawl and the development of agricultural landscapes have had profound impacts on the distribution of organisms and the ecology of ecosystems, promoting certain species and processes that have thrived in highly modified and managed landscapes, while diminishing or eliminating others (Vila & Ibáñez 2011). Aquaculture development in sheltered coastal environments results in an ongoing proliferation of artificial structures outside urban areas (Gentry et al 2017). In terms of their role as marine habitats, aquaculture developments differ categorically from urban maritime sprawl. The outcome is that marine farming developments provide extensive areas of homogenous nearshore novel habitat, with a range of potential positive and negative repercussions for regional-scale distribution of species and possible effects on ecological processes that have not been well explored to date (McKindsey et al 2007, Lacoste & Gaertner-Mazouni 2015)
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